Thin film transistor liquid crystal displays (TFT-LCDs) have characteristics including small size, low power consumption, no radiation and the like, and dominate the current flat panel display market. The TFT-LCD mainly consists of an array substrate and a color film substrate arranged in cell alignment, wherein a gate layer (including a gate and a is gate line), a source/drain layer (including a source, a drain and a data line) and a pixel electrode are formed on the array substrate.
However, in the existing array substrate, there is a large coupling capacitance between the gate layer and the source/drain layer due to the presence of an overlapping region therebetween, resulting in insufficient TFT driving capability of the pixel and slow charging speed of the pixel.
This coupling capacitance is liable to cause a large variation (Δ Vp) in the pixel voltage, so that the set pixel voltage written through the data line changes after the TFT is turned off. Such a change in turn causes the gray scale displayed by the pixel in the end to deviate from the gray scale desired to be expressed by the originally written voltage, and causes the voltage having symmetrical positive and negative polarities which is originally written by the data line to deviate downward to generate DC residue.